A Dufaycolor colour transparency of the Ponte Vecchio in Florence, Italy, taken by an unknown photographer in about 1937. Spanning the River Arno, this is the oldest and most famous bridge in Florence. The Dufaycolor process was introduced as cine film in 1932 and as rollfilm for still photography in 1935. Based on Frenchman Louis Dufay's (1874-1936) Dioptichrome process of 1908, it was the last 'additive' colour process to be marketed and consisted of a very fine, regular filter screen made up of red, green and blue lines printed on a film base. Dufaycolor was popular with both amateur and professional photographers and survived until the 1950s.
© Kodak Collection / National Science & Media Museum / Science & Society Picture Library